Karl Leonhard and the re-evaluation of Emil Kraepelin’s diagnostic concept of manic-depressive psychosis

The re-evaluation of Kraepelin’s diagnostic concept of “manic-depressive psychosis” culminated in 1957 with the publication of Karl Leonhard’s monograph, The Classification of Endogenous Psychoses. In his classification, Leonhard integrated the contributions of Wernicke, Kleist and his collaborators with his own findings and conceptualizations.

Leonhard began with his research in the late 1920’s, after graduating from medical school, in 1928. By 1936, the year he joined Karl Kleist’s Department of Psychiatry at Goethe University in Frankfurt, he had already published some findings in “episodic psychoses”, “atypical psychoses” and “defect schizophrenias" which were in line with Karl Kleist’s reports (Kleist 1911, 1923, 1925, 1928; Leonhard 1931, 1934, 1936).

During the Frankfurt years, Leonhard collaborated with Kleist and Edna Neele in studying “phasic psychoses”, i.e., “episodic psychoses” with full remissions between episodes, and was instrumental in the conceptualization of findings in this project. It was in the course of this research that Kleist’s (1928) introduced his original concept of “bipolarity”, a combination of two “unipolar” syndromes (“manic psychosis”, “melancholic psychosis”) and “polymorphous-bipolar psychoses” (“manic-depressive psychosis”) (Kleist 1943; Leonhard 1943). It was also in the course of this research that it was recognized that “polymorphous-bipolar psychosis” was not restricted to “manic-depressive illness of affect” but also included other “psychoses”, which were based on other “pairs of syndromes” like “manic-depressive psychosis” in which the “elementary symptom” was not in mood, but in other areas of psychopathology (Teichmann 1990). By the time of the 1940’s, several such ”psychoses” were described and referred to as “cycloid psychoses” by Kleist (Fünfgeld 1936; Kleist 1911, 1925, 1928, 1953; Leonhard 1939).

The currently used, Latin-derived terms, “unipolar” and “bipolar” were coined, in 1948, by Leonhard and the distinction between “unipolar depression” and “bipolar depression” in reference to “mood disorders” was supported by Neele’s “epidemiological genetic” findings reported in her monograph on “Phasic Psychoses”, in 1949 (Angst and Grobler 2015). It was also in Neele’s report, in which Kraepelin’s (1913) all embracing diagnostic concept of “manic-depressive psychosis” was deconstructed into various forms of “phasic psychoses”: “simple-unipolar” and “polymorphous-bipolar” (Teichmann 1990).

The concept of “polarity” became central, but not an exclusive organizing principle in Leonhard’s (1957) re-evaluation of Kraepelin’s (1913) “manic-depressive psychosis”. On the basis of “polarity”, he split it into “bipolar manic depressive disease” and “unipolar phasic psychoses”, and with consideration of Wernicke’s (1899, 1900) “mental structure”, he separated the “cycloid psychoses” from “manic depressive disease” and divided the “cycloid psychoses” into “excited-inhibited confusion psychosis”, “anxiety-happiness psychosis”, and “hyperkinetic-akinetic motility psychosis”. Then, on the basis of “totality”, the organizing principle introduced by William Cullen (1769, 1772, 1776), he separated “pure mania” and “pure melancholia”, both “universal” diseases, from the “pure euphorias” and “pure depressions”, in which the “mental structure” was only partially affected. Finally, on the basis of Wernicke’s (1893) “elementary symptoms”, he distinguished five distinct forms (unproductive, hypochondriacal, enthusiastic, confabulatory and non-participatory) of “pure mania”, and five distinct forms (harried, hypochondriacal, self-torturing, suspicious and non-participatory) of “pure depression”.

In 1957, at the time it was first published, Leonhard’s classification had already some support, from epidemiological genetic findings, as indicated before (Neele 1949). Yet, it was only in 1964, one year before the publication of the third edition of the text, in 1965, that Leonhard succeeded to demonstrate that his diagnoses of “cycloid psychoses” were “catamnestically correct” (Leonhard and Trostorff 1964); and it was only, in 1966, two years before the publication of the fourth edition, in 1968, that Jules Angst (1966) and Carlo Perris (1966) independently demonstrated that “bipolar depression” and “unipolar depression” were “separable”. The signal difference between the two populations was that patients with “bipolar depression” had a significantly higher rate of “psychoses” among their relatives than patients with”unipolar depression”. The (epidemiological) genetic distinctiveness of “unipolar depression” and “bipolar depression” was further substantiated, in 1969, by Winokur, Clayton and Reich.

It was only well after the publication of the 6th edition of Leonhard’s monograph, in 1986, the last edition published during his life time, that findings relevant to the distinctiveness of “unipolar mania” and “bipolar mania” emerged. First, in three independent clinical epidemiological studies, it was found that “unipolar mania” had an earlier onset and was characterized by fewer episodes and lower comorbidity with anxiety disorders than “bipolar mania” (Merikangas et al 2012; Pacheco Palha and Arrojo 2009; Young, Marek and Patterson 2009). Then, Yazici and Cakir (2012) noted that patients with “unipolar mania” were less responsive to lithium therapy than patients with “bipolar mania”, and Grobler, Roos and Bekker (2014) reported that patients with “unipolar mania” were prescribed more “neuroleptics” than patient with “bipolar mania”. Finally, in an epidemiological genetic study, Merikangas and associates (2014) found the familial aggregation of depression in relatives of “depressed probands” much lower than the familial aggregation of mania in the relatives of “manic probands”, indicating the genetic independence of maia from depression that “unipolar mania” and “bipolar mania” are distinct diseases (Angst and Grobler 2015; Hicki3 2014 ).